Hollow needle



B. E. BALDWIN ETAL Jan. 1, 1963 HOLLOW NEEDLE 2 Sheets-Sheet 1 FiledJan. 27, 1960 PRIOR ART PRIOR ART 1 Jan. 1, 1963 B. E. BALDWIN ETAL3,071,135

HOLLOW NEEDLE EJ6112 2: r5 15:1 cu-e 675a zfduz z'r-z fay agz'rzoZer-zme/sy 2 a m 2 w Z T U n 1 A 6 3 R z a 2 N n w N EA W 8 WM E Q MM E0 2 mmE] E m o V m 9 m 7/ u .j m J d u m 0 3,071,135 HOLLQW NEEDLE Brian E.Baldwin and Ray S. Lindenrneyer, Evanston, IlL, assignors toManufacturing Process Laboratories, inc, Chicago, 11th, a corporation ofIllinois Filed Jan. 27, 196i), Ser. No. 4,985 3 Claims. (i.]t28-221)This invention relates to a hollow needle, and more specifically, to animproved and highly effective non-coring hypodermic needle.

The problems and possible dangers of coring in the use of hypodermicneedles have come to light only in recent years. As a hypodermic needlepenetrates a tissue layer or membrane, the sharp leading edges of thebeveled point cut an arcuate slit and, if the flap defined by thiscurved slit gets into the path of the needles sharpened heel edges, aminute plug or core of tissue may be severed from the fiap. Such a core,if cut from a flap of skin, is likely to be transplanted in a muscle,vein or tissue under the skin, depending on the final position of theneedle tip at the time of fluid injection. In effect, the core becomes askin graft when transplanted into muscle or under-the-skin tissue andmight produce a cyst or subcutaneous infection. In a case of venousinjection, it is at least theoretically possible for the skin core tolodge in the tiny reins of the lungs, thereby causing an embolism.

Coring may also occur when a hollow needle is forced through themembrane of a vial or other container. In such a case, the smallparticle of rubber is either drawn into the lumen of the needle or dropsdownwardly into the vial. Even if the latter should occur, there is thedanger that the detached core may later be drawn into the syringe as itis manipulated to withdraw the vials contents and, where a multidosevial is used, it is believed apparent that the likelihood of drawingsuch a core into the syringe and thereafter injecting it into a patientis considerably increased.

EiTorts have been made to develop non-coring needles but the results ofsuch efforts have been generally unsatisfactory. For example, it hasbeen thought that if the heels of needles were depressed slightly thenthe sharpened edges of those heels would pass through the arcuateopenings cut by the needles leading edges and would not sever the tissueflaps or cut into the walls of the openings. However, the mechanicaloperation of physically depressing the heel of a small bore needle is anextremely delicate one and, at best, is a time consuming and expensiveprocedure requiring extreme precision and control. Furthermore, it hasbeen found that mechanically depressing a needle heel does not in itselfsubstantially reduce the coring tendency of that needle. Instead, itcreates a new problem because of the constriction of the needle lumenand the resulting interference with the smooth flow of liquidtherethrough.

Since a needle with a depressed heel has certain inherent disadvantagesand does not efiectively solve the coring problem, some workers in thefield have attempted to overcome the problem by a different operationwherein a needle is ground to provide a step or shelf in the area of itsheel, the previously sharpened heel edges about the lumen opening beingobliterated and the rising portion of the step providing a blunt forwardface. Such a needle naturally requires increased force for penetrationsince the blunt surface ordinarily encounters considerable resistanceupon engagement with the flap cut by the needles tip edges. Moreover, asfar as coring is concerned, it has been found that even such a radicaldesign as this not only has a tendency to core but also appears toabrade small particles from the outer surface of the flap as the needleis inserted.

hired rates Fatent HQC A problem somewhat related to coring and onewhich must also be considered in connection with needle point geometryconcerns the effects upon needle penetration force characteristicsincident to variations in needle point configuration. It has been foundthat when a conventional needle penetrates a membrane the force requiredfor insertion increases until the outer perimeter of the needle heelpasses through the membrane opening. From then on, no further expansionof the membrane opening is required for passage of the needle and thepenetration force drops to a generally constant value. Since the maximumpenetration force required for insertion of any given needle into tissuebears an important relation to the pain caused by such insertion, it isapparent that any changes in needle configuration intended to reduce thecoring problem must not at the same time increase the needles resistanceto penetration. Conversely, a noncoring needle is of little practicalvalue if the structural changes responsible for its non-coringcharacteristics result in a relatively high penetration force peak.

Accordingly, a main object of the present invention is to provide ahighly effective non-coring needle of simple and inexpensiveconstruction which overcomes all of the aforementioned defects anddisadvantages of previous needles. Specifically, it is an object toprovide a noncoring needle in which the structural features responsiblefor preventing coring do not reduce its penetration characteristics,impair the flow of fluid through its lumen, or adversely affect itsbehavior in any other material respect. Another object is to provide animproved needle which will not abrade a membrane or tissue duringinsertion and which has a relatively low penetration force peak ormaximum.

Other objects will appear from the specification and drawings in which:

FIGURE 1 is an enlarged plan view showing the end portion of a needleembodying the present invention; 1

IFIGURE 2 is a side elevational view of the needle illustrated in FIGURE1;

FIGURE 3 is a further enlarged end elevational view showing the needletip and heel construction;

FIGURE 4 is an enlarged cross sectional view taken along line 44 ofFIGURE 1;

FIGURE 5 is a sectional view of a vial having a conventional needle(lancet) partially inserted through the membrane thereof;

FIGURE 6 is an enlarged longitudinal sectional view of a conventionallancet as it penetrates a relatively thick resilient membrane;

FIGURE 7 is a greatly enlarged longitudinal sectional view of a needleembodying the present invention, the View being taken along line 7-7 ofFIGURE 1;

FIGURE 8 is a graph representing the force patterns for needlepenetration of a membrane.

In the structure illustrated in the drawings, the numeral It) generallydesignates a hollow needle or cannula with a lumen ll of uniform crosssection extending longitudinally therethrough. In the illustrationgiven, the tubular needle is cylindrical in shape and the lumen iscircular in cross section. At one end, the needle is provided with abeveled front face =12 while at its opposite end it may be provided witha suitable adapter 12a, indicated by broken lines in FIGURE 1, forconnection to a hypodermic syringe.

As is well known in the art, a pointed needle is formed by firstgrinding or otherwise treating a tube of small bore so that its frontface 12 lies along a plane angled with reference to the tubeslongitudinal axis. Preferably, but not necessarily, the tube is thenrotated about its longitudinal axis and is subjected to additionalgrinding or treating operations to dforin beveled side faces 13 angledwith reference to the plane of the main face 12.

The side bevels result in the formation of a sharply pointed tip 14 andthereby reduces the force necessary for needle penetration. In theabsence of the side bevels, the needle tip would be curved rather thanpointed since it would constitute a portion of the outer ellipticalperimeter of the main bevel 12. As far as the present invention isconcerned, the needle may or may not be provided with side bevelsalthough the provision of such bevels is desirable for the reasonalready given.

The portion of a needle face behind the midpoint of the lumen opening isgenerally referred to as the heel of the needle. It is the constructionor configuration of heel surface 15, and its outer perimeter, as well asthe inner perimeter or edge portion of that heel bordering the lumenopening 16, with which the present invention is concerned.

The conditions which give rise to coring are illustrated in FIGURES 5and 6 of the drawings. FIGURE 5 shows a conventional lancet A as itpenetrates the flexible diaphragm B of a vial C. The flap cut by theleading edges of the lancet flexes downwardly to accommodate the needleand, in so doing, bears against the rear heel edge of the downwardlymoving needle. Should the heel edge of the needle cut into the membraneflap, a small plug of rubber may be detached from that flap and eitherpass into the needle lumen or drop downwardly into the vial.

The thickness, smoothness, toughness and flexibility of the membrane allhave a bearing on the tendency to form detached plugs or cores uponneedle penetration. For instance, if the membrane is relatively thin andflexible, the flap will be more likely to yield upon contact with therear edge of the lumen rather than be out by that rear edge. On theother hand, if the diaphragm or tissue is relatively thick, as indicatedin FIGURE 6, the heel edge of the needle may engage the outer surface ofthe membrane before a flap is completely formed with the result that theheel edge of the conventional needle A is more likely to cut or scrapethe membrane directly in its path and thereby abrade particles from themembrane or form a detached plug of material.

Referring again to FIGURES l4 and 7 illustrating the needle vitembodying the present invention, it will be seen that heel is dished toprovide an external recess '17. While this concavity might be referredto as a depression, it is important that there is no corresponding bulgeor deformation beneath the heel within the needle lumen. Instead, theinternal cross sectional dimensions of the needle remain uniform and therecess arises because some of the material from which the needle isformed has been removed from the heel.

The external recess 17 extends rearwardly a limited distance behind therear edge portion 18 of the lumen opening 16 and, as shown most clearlyin FIGURES 2, 3 and 7, rear edge portion 18 is rounded (when viewed insection) and dulled. The smoothly rounded surface of edge portion 18merges with the smooth surface of heel recess 17 and the outer limits ofthe generally lozengeshaped recess merge smoothly and without sharpangles into the surface of planar face 12. Upon needle insertion, shouldcontact occur between rear edge portion 18 and a tissue or membrane, thesmooth dull surfaces of that edge portion will tend to slide over ratherthan scrape or cut into the membrane or tissue, thereby reducing theresistance to needle penetration which might otherwise be caused bysharpened rear lumen edges (FIGURE 6) and eliminating the dangers ofplug cutting. Further, it will be noted that these important advantagesare achieved without lumen constriction and the undesirable effectsthereof.

While various means might be used to remove material from the heel andrear edges of the lumen opening, We have found that such an operationmay be performed simply and quickly by the carefully cont-rolledapplication of any of a variety of commercial etchants. Etching also hasat least one other important advantage in connection with the removingof metal from the needle heel and lumen edges; it leaves the recessedheel and the rounded edges of the lumen opening with smooth glass-likesurfaces. Also, the recess surfaces merges smoothly with the rear lumenedges and with the remainder of the heel sunface so that there are nosharp edges or abrupt slope changes in the vicinity of the needle heelwhich might tend to cut or abrade the edge portions of an opening formedby insertion of the needle point.

Upon insertion of needle 10 into a tissue or membrane, the dull andsmooth rear edges about the lumen opening slide over and push asiderather than cut the membrane or tissue so that no core is formed, evenwhere the body wall or membrane is relatively thick as in FIGURE 6. Thefact that a substantial portion of the heel surface as well as the rearedge of the lumen opening are spaced within the circumferential limitsof the needle reduces to some extent the likelihood of contact betweenthe tissue or membrane and surface 17 or edge portion 18. However, evenwhen such contact occurs, the dull and smooth rear edges about the lumenopening tend to push the material away rather than out into or abradethe surface thereof.

Extensive tests have been undertaken which demonstrate the non-coringproperties of a needle embodying the present invention and also showingits superiority in this regard over other needles known in the art. Inone such test, a double side bevel needle (lancet) embodying theinvention was compared with 26 other needles having different needlepoint geometry. Specifically, the needles with which comparison was madeincluded needles having points with single bevels, double side bevels(lancets), single side bevels and back bevels. In addition, such needleshad various other characteristics such as depressed heels, step-cutheels, deflected points (full and half bend) and different bevel angles.For test purposes, all needles were of increased size (10 magnificationof 18 gage needles). Three inch squares of A inch thick rubber with a 50durometer reading were placed in a frame and were punctured by eachmodel needle. Three tests were made with each model pointfirst withthree thicknesses of rubber, next with two pieces, and finally with onepiece. When all tests were made, the resulting puncture configurationswere studied and the size of core or the tendency to cut cores noted.

In the tests involving the needle embodying the present invention, nocores were cut at all. All of the remaining needles cut cores in atleast one test of each test series, with the exception of one needle ofthe group of depressed heel lancets which made substantial cuts in therubber flap with its lumen edges but did not completely detach the plugfrom that flap. In summary, the needle embodying the present inventionwas more effective by a considerable margin than any of the needlestested in its ability to penetrate without coring.

An important aspect of the present invention lies in the fact that, inaddition to its non-coring properties, needle It) has a relatively lowpenetration force peak. Referring to the graph of FIGURE 8, solid line20 represents a typical penetration force curve for a conventionalhypodermic needle. The dip behind the first small pea" 21 represents theslight reduction in applied force which frequently occurs the moment thesharpened tip of the needle breaks through or cuts into a tissue ormembrane. Thereafter, the force required for needle penetrationprogressively increases until the maximum force at peak 22 is exerted.This major peak in applied force occurs when the rear portion of theneedle heel--that is, the outer rear perimeter of the elliptical mainbevel or faceis about to pass through the opening in the membrane. Assoon as the outer rear edge of the needle face passes through theopening, there is a drop in the force required for further needlemovement through the opening.

Unlike a conventional needle, needle 10 of the present invention doesnot have an abrupt change in contour at a junction between the beveledheel surface and the cylindrical surface of the tubing. Instead, therear surface portion of the main face 12 curves or blends smoothly intothe tubular surface therebehind. In addition, the surface of the tissueflap recess 17 blends smoothly with the remainder of the heel surfacesand with the cylindrical surface of the needle behind face 12, therecess extending rearwardly into the cylindrical outer surface of theneedle a substantial distance behind the beveled surface 12.

The blending of the heel surfaces with the needles cylindrical surfaceand the provision of the tissue fiap recess or groove 17 which relievestension of the membrane flap results in a needle having a relatively lowpenetration force peak. This is represented in the graph of FIGURE 8 bybroken line 23. It has been found that the maximum penetration forcerequired for insertion of a needle embodying the present invention issubstantially less than the maximum force for a conventional needlehaving the same bevel angles.

The importance of this difference in maximum penetration force becomesapparent when it is understood that pain of injection is associated witha pressure threshold. Unless a threshold force level is reached, apatient may feel no pain at all when a needle is inserted into his body.While this threhold value varies depending upon the area of injectionand also varies for different individuals, it is neverthelesssignificant that a needle having relatively low maximum penetrationforce characteristics may in many instances produce painless injection.

It should be noted that the graph in FIGURE 8 represents the penetrationforce curves of needles as they penetrate a thin membrane, in contrastto relatively thick membranes or body tissues. The drop off in maximumpenetration force does not occur until the heel of a needle has passedcompletely through the membrane or tissue and therefore, in the case ofinjection into a patients body, no reduction in the maximum force levelwould be expected until forward movement of the needle ceases.

While in the foregoing, we have disclosed an embodiment of the presentinvention in considerable detail for purposes of illustration, it willbe understood by those skilled in the art that many of these details maybe varied without departing from the spirit and scope of the invention.

We claim:

1. A non-coring needle having a beveled front face and having a lumen ofuniform cross section, said face providing a lumen opening of crosssectional dimensions no smaller than the cross section of said lumen,said face providing behind the lumen opening a heel surface merging witha smooth rounded and dull rear edge portion of said lumen opening, saidheel surface also being dished to provide a smooth external recessextending rearwardly a limited distance behind said dull rear edgeportion.

2. In a hollow needle having a lumen of uniform cross section and havinga beveled front face providing a lumen opening of cross sectionaldimensions no smaller than the cross section of said lumen, said frontface including a heel surface behind said lumen opening in said face,said needle having a rounded, smooth and dull edge defining a rearportion of the lumen opening, said heel surface being dished to providea smooth-surfaced external recess extending rearwardly a limiteddistance behind said dull rounded edge.

3. A hollow non-coring needle having a lumen of uniform cross sectionand having a beveled front face providing a lumen opening of crosssectional dimensions no smaller than the cross section of said lumen,said face E also providing a heel surface behind said lumen opening insaid face, said heel being externall dished to provide a heel portion ofreduced wall thickness, the rear edge portion of said lumen openingadjacent said heel providing a. smooth, rounded and dull surface.

4. A cylindrical hollow needle having a lumen of uniform diameterthroughout and having a front face angled with reference to the needleslongitudinal axis, said front face being provided with a lumen openingof cross sectional dimensions no smaller than the diameter of said lumenand having a heel surface behind said opening, said heel surface beingdished to provide a smooth external recess in the Wall of said needlebehind said opening, the rear edge of the lumen opening adjacent saidheel being dull and smooth.

5. A cylindrical hollow non-coring needle having a lumen of uniformdiameter throughout and having a front face angled with reference to theneedles longitudinal axis, said front face providing a lumen opening ofcross sectional dimensions no smaller than the diameter of said lumenand having a heel surface behind said opening, the edge portion of theneedle about the rear of the lumen opening being elliptical in contourand having a smooth rounded cross-sectional configuration, said heelsurface merging with the surface of said edge portion and being dishedto provide a smooth-surfaced external recess extending rearwardly alimited distance behind said lumen opening.

6. A non-coring needle having a beveled front face and having a lumen ofuniform diameter, said face providing a lumen opening having crosssectional dimensions no smaller than the diameter of said lumen, saidface providing behind the lumen opening a heel surface merging with asmooth rounded and dull rear edge portion of said lumen opening, saidheel surface being dish-ed to provide a smooth external recess extendingrearwardly behind said dull rear edge portion and beyond the outerperimeter of said front face.

7. In a hollow needle having a lumen of uniform cross section and havinga beveled front face providing a lumen opening of cross sectionaldimensions no smaller than the cross section of said lumen, said frontface including a heel surface behind a lumen opening in said face, saidneedle having a rounded, smooth and dull edge defining a rear portion ofthe lumen opening, said heel surface being dished to provide asmooth-surfaced external recess extending rearwardly behind said dullrounded edge and beyond the outer perimeter of said front face, saidheel surface blending smoothly and gradually into the outer rear surfaceof said needle beyond the perimeter of said beveled front face.

8. A cylindrical hollow needle having a beveled front face and having alumen of uniform cross section, said front face providing a lumenopening having cross sectional dimensions no smaller than the crosssection of said lumen, said face providing a heel surface behind thelumen opening therein, said heel surface being dished to provide asmooth-surfaced external recess and blending smoothly and gradually intothe rear cylindrical surface of said needle beyond the perimeter of saidbeveled face.

References Cited in the file of this patent UNITED STATES PATENTS2,560,162 Ferguson July 10, 1951 2,711,733 lacoby June 28, 1955 FOREIGNPATENTS 137,455 Great Britain Ian. 15, 1920 489,535 Canada Ian. 13, 1953

8. A CYLINDRICAL HOLLOW NEEDLE HAVING A BEVELED FRONT FACE AND HAVING ALUMEN OF UNIFORM CROSS SECTION, SAID FRONT FACE PROVIDING A LUMENOPENING HAVING CROSS SECTIONAL DIMENSIONS NO SMALLER THAN THE CROSSSECTION OF SAID LUMEN, SAID FACE PROVIDING A HEEL SURFACE BEHIND THELUMEN OPENING THEREIN, SAID HEEL SURFACE BEING DISHED TO PROVIDE ASMOOTH-SURFACED EXTERNAL RECESS AND BLENDING SMOOTHLY AND GRADUALLY INTOTHE REAR CYLINDRICAL SURFACE OF SAID NEEDLE BEYOND THE PERIMETER OF SAIDBEVELED FACE.